Abstract
Abstract We compare magnetic field measurements taken by the FIELDS instrument on board Parker Solar Probe (PSP) during its first solar encounter to predictions obtained by potential field source surface (PFSS) modeling. Ballistic propagation is used to connect the spacecraft to the source surface. Despite the simplicity of the model, our results show striking agreement with PSP’s first observations of the heliospheric magnetic field from ∼0.5 au (107.5 R ⊙) down to 0.16 au (35.7 R ⊙). Further, we show the robustness of the agreement is improved both by allowing the photospheric input to the model to vary in time, and by advecting the field from PSP down to the PFSS model domain using in situ PSP/Solar Wind Electrons Alphas and Protons measurements of the solar wind speed instead of assuming it to be constant with longitude and latitude. We also explore the source surface height parameter (R SS) to the PFSS model, finding that an extraordinarily low source surface height (1.3–1.5 R ⊙) predicts observed small-scale polarity inversions, which are otherwise washed out with regular modeling parameters. Finally, we extract field line traces from these models. By overlaying these on extreme ultraviolet images we observe magnetic connectivity to various equatorial and mid-latitude coronal holes, indicating plausible magnetic footpoints and offering context for future discussions of sources of the solar wind measured by PSP.
Highlights
Parker Solar Probe (PSP; Fox et al 2016) is a NASA mission intended to revolutionize our understanding of the solar corona by becoming the first spacecraft to measure its outer layers in situ
It takes synoptic maps of the radial magnetic field at the photosphere and a value for the source surface height parameter RSS. From these data it produces a full 3D magnetic field within the modeled volume, as well as a utility to trace individual magnetic field lines through the model solution. This input/ output mapping is illustrated in Figure 3(A) which shows selected 3D field lines produced by pfsspy, the extent of the model, and the photospheric map that seeds the model
We present the results of comparison of the above modeling to PSP data
Summary
Parker Solar Probe (PSP; Fox et al 2016) is a NASA mission intended to revolutionize our understanding of the solar corona by becoming the first spacecraft to measure its outer layers in situ. The fundamental science objectives are to (1) trace the flow of energy that heats and accelerates the solar corona and solar wind, (2) determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind, and (3) explore mechanisms that accelerate and transport energetic particles. Central to its science goals is PSP’s record-breaking orbit. PSP launched on 2018 August 12 and, after its first Venus gravity assist, entered into the closest-grazing heliocentric orbit ever reached by an artificial satellite.
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